Speculation ran rampant as to what the ghostly image was: a freighter ship? Perhaps Milwaukee?

Here's an argument for a freighter using shipping data:

The ship was apparently Undaunted, which closer matched the timeline, according to an earlier comment.

The Herbert C. Jackson should have been visible just off the shore from about noon (to the southwest) to 2pm (to the northwest) as it passed by from Burns Harbor heading north, off the coast of Frankfort by 10pm local time. The ship has rather similar characteristics to the one in the photo with its front end on the right, rear end on the left as it heads north.

Or you could buy into the Milwaukee argument:

It’s the Milwaukee sky line due to climatic conditions you can see Milwaukee clearly but this typically happens at night and you see the lit up skyline never have seen a daytime picture like this and I’ve only witnessed it once at night in the same location